The invention relates to a control signal transmitting apparatus especially for aircraft. Such control signals are to be transmitted to the control surfaces, for example, the flaps of the elevator assembly, the rudder assembly, and so forth. The transmission is to be accomplished by a passive conductor system.
It is generally known that control signals in an aircraft are transmitted in response to control movements made by the pilot, for example to control the rudder, by mechanical means such as cable pulls, linking rods, rotational shafts, or combinations of such mechanical means. Depending on the type of application, these devices are supplemented by hydraulic or electrical drive means. It is further known in connection with large volume aircraft to employ servo-control systems. Due to the mechanical coupling means interposed between certain rudders in such control systems the operational patterns are positively or rigidly determined. For example, the following operational patterns are so determined: operation of the elevator assembly takes place always symmetrically, operation of the ailerons takes place always in a non-sysmmetrical manner, operation of the landing flaps or air brake flaps always takes place symmetrically.
These fixed operational patterns have the disadvantage that, for example, upon failure of a certain rudder, the remaining still operational rudder might possibly not be available for use in re-establishing the maneuverability. If military considerations are taken into account the above mentioned mechanical control systems have a further disadvantage resulting from their vulnerability. Thus, for these purposes electrical servo-control systems have been used in which the transmission of control signals takes place through passive conductors such as coaxial cables. In such a system it is possible to provide the individual operational circuits including the cables leading to the individual adjustment members in a redundant manner, for example in quadruplicate. Thus, such an operational circuit remains, for example, still operational even if three of the respective cables have failed, for example, as a result of combat action. However, the provision of redundant signal transmitting circuit means has, among others, the following weak points. Such systems are sensitive to electro-magnetic disturbing fields such as lightning impact, short circuits and the like. An intermeshed cable network cannot be realized without active elements at the nodal points of the network due to transit time effects and reflection effects. Further, due to the just mentioned effects, the wiring may be carried out in practice only in the form of function related wiring strands. This means that, for example, in a quadruplicate redundancy systemn four cables are required for each adjustment member to be controlled. Additionally, this type of wiring results in a substantial cable weight if cables with a low damping coefficient are used.
According to the magazine "Electronik Praxis" (Electronic Practice), Vol. 11, pg. 34, 1979, it is known to use light conductors for the assembly of data bus systems, for example, on board ships or aircraft or for controlling industrial processes. In a narrower sense the term "data bus" means a conductor for transmitting or relaying of information to which all subscribers are connected. According to the above article, such systems may be constructed as so-called radial or star-bus or as a T-bus. In a radial or star-bus system all connecting conductors converge in a so-called star-coupling member. In a T-bus system each subscriber is connected to the data-bus by a T-coupling member. The light conductor technique has substantial advantages with regard to its use in the control systems of an aircraft, for example, with regard to the weight and reliability. Nevertheless, the radial or star-bus concept as well as the T-bus concept have the disadvantage that each subscriber or rather, each controlled member is connected to the remainder of the system through but one conductor. It follows, that upon failure of such single conductor the functions of the respective subscriber or controlled member must also fail. In connection with the control of an aircraft this would mean that upon failure of a corresponding conductor, for example, due to a localized damage as a result of the failure of other components, possibly a vital control function could be eliminated.